1. Field of the Invention
Applicant's invention relates to the field of construction of double-walled vessels made of woven fiber-reinforced laminated materials; including boat hulls, boat bulkheads, and containers or tanks for holding liquids.
2. Background Information
Presently vessels requiring the use of strong walled materials are made from a number of different molded fiber-reinforced laminated walled structures. One type of vessel, such as a boat hull, is generally composed of a solid thick wall having a thickness of approximately 3/4 inch providing a structure with excellent strength characteristics; however, this thick walled vessel is heavy and expensive to make particularly when it is made of solid fiber-reinforced materials. Lighter weight double-walled vessels, having an intermediate space between the walls filled only with polyethylene netting, have been used as underground fluid containing tanks; however, the strength of this vessel is greatly reduced from that of the solid walled structure because the separate walls are not effectively joined for combined strength.
Other double-walled fiberglass vessels have been constructed having an intermediate layer of balsam wood between the separated walls. Such double-walled, balsam filled vessels are expensive, difficult to mold to contours, tend to absorb water, and have limited strength characteristics as compared to the previously discussed solid double-walled structure. Additionally, some vessels for marine use have also used a core material of rigid polyurethane foam with polyester fiberglass outer skins between the two walls; however, expensive molds are required to produce such a core and the core generally has a very low core shear strength.
The present invention provides a strong double-walled vessel by bonding an intermediate single woven member containing a plurality of parallel longitudinally extending cylindrical members and a plurality of parallel fibers woven about the cylindrical members and extending perpendicularly to the cylindrical members between the first inner and the second outer walls. The cylindrical members are retained in the woven member. This configuration provides a vessel with a double-walled laminated frame equivalent in strength to the solid double-walled structures but it contains 50% less raw materials and therefore is less expensive to construct.
The double-walled laminated frames of the vessels of the present invention may contain cylindrical members, which may be hollow, plastic tubes; or solid, foam pipes depending upon the final intended use of the vessel. Further, the vessel of the present invention is prepared on a mold by spraying up one of the walls on the mold, followed by laying the already prepared intermediate single woven member and then spraying up the other wall on the mold.
The double-walled, fiber-reinforced laminated vessels of the present invention provide advantages over the prior art double-walled, laminated vessels because they have equivalent strength to a solid walled vessel and are lightweight yet cost less than prior art vessels as a result of using 50% less raw material. The vessels of the present invention may be used for numerous purposes in the marine industry and in the container or tank industry. The use of double-walled vessels of the present invention in these industries is important because should either the interior wall or exterior wall of the vessel of the present invention fail or be punctured, then the other wall serves as a backup to retain the fluid in the vessel. This is particularly important when such vessels are boat hulls or underground storage tanks retaining gasoline, oil, or other potentially toxic fluids. The double-walled vessels also allow the integrity of the walls to be monitored when the vessel serves as an underground storage tank.